1. Field of the Invention
The present invention relates to an apparatus for and a method of controlling a fuel injection control, applied to an engine provided with a variable valve mechanism, which varies an opening characteristic of an inlet valve.
2. Description of the Related Art
Japanese Laid-Open (Kokai) Patent Application Publication No. 2005-248883 discloses an engine provided with a first injection valve that injects fuel into an inlet passage on an upstream side of an inlet valve, a second injection valve that directly injects fuel into a cylinder, and a variable valve mechanism that changes a lift amount and/or valve timing of the inlet valve.
This publication further discloses the technique that, as the lift amount of the inlet valve is decreased and/or as a valve-opening time of the inlet valve is delayed from an inlet top dead center, a ratio of an amount of fuel injected from the first injection valve to a total fuel injection amount is decreased, and a ratio of an amount of fuel Injected from the second injection valve to the total fuel injection amount is increased.
In the case where an intake air amount is controlled by the variable valve mechanism, because an inlet-valve opening characteristic is gradually changed in a transient state even after the opening timing of the inlet valve is started, the intake air amount in the intake stroke is decided and fixed at the point of closing timing of the inlet valve.
On the other hand, in order to enhance homogeneity of an air fuel mixture, it is necessary to inject the fuel in an earlier timing.
Therefore, a lag occurs between timing where the intake air amount is finally fixed and timing where the fuel injection amount is fixed. When the variable valve mechanism is operated to change the inlet-valve opening characteristic after the fuel injection amount is fixed, a difference is caused between the actual intake air amount and the intake air amount, which have been decided in accordance with the fuel injection amount, and accordingly the air fuel ratio might deviate from the target air fuel ratio.